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Difficulty: MediumContinuous and Discontinuous Variation

Human phenotypic traits exhibiting discontinuous variation, such as the ABO blood group system and tongue rolling ability, are governed by polygenic inheritance and can be significantly modified by environmental factors during an individual's lifetime.

Answer: Answer

Answer

The statement is False. Discontinuous variation is characterized by monogenic inheritance producing non-overlapping phenotypic categories that are not modified by environmental factors.
The statement is false because discontinuous variation results from monogenic inheritance, producing clear-cut phenotypic classes that are completely independent of environmental factors.

Step-by-Step Solution

1
Analyze the phenotypic expression of the traits listed (ABO blood group and tongue rolling).
These traits fall into distinct, non-overlapping categories without intermediate forms.
Clear-cut distinct classes are the hallmark of discontinuous variation.
2
Evaluate the genetic control and environmental influence described in the statement.
Discontinuous traits are governed by monogenic inheritance (single gene or allele pairs) and are unaffected by environment, whereas polygenic inheritance and environmental sensitivity characterize continuous variation.
Distinguishing the genetic basis (monogenic vs. polygenic) and environmental interaction is essential to classifying variation types accurately.

Key Concept

Genetic basis and environmental stability of discontinuous variation
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Topics

Continuous and Discontinuous Variation

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